Electrical apparatus



y 1953 w. CHURCH ELECTRICAL APPARATUS Filed Sept. 23, 1950 Patented May 12, 1953 iNflTf-ED EN T Q FSF IE-E ELECTRICAL APPARATUS Walter3Lyman Ghnrh, Flint, Mich, assignor to General Motors-f florporafion, Dayton, :Ohio, a

corporation ofDelaware Application Sep'ten'ib'or 23, 1950', SeriaINo. 186,477

" 5 Claims. (015175- 335) This invention relates to electrical apparatus and more "particularly to time new relays hav in'ga delay of a-iex'wmilliseconds. It' part'ioularly' relates to timedlay relays such as may be "used toeha'nge the "circuit in 'a'g'low plug ignition system to 'reduce the high *energycurr'ent as soon as the glowplug 'has been hea tel to its operating temperature.

It is an 'o'bfi'ect of my invention to provide-an accurate reliable time delay relay in which a time delay of "a "few 'nii'lliseconcls "is provided through the use of "an electrical conducting means *associ'aiteii with the ii'onmircuit -f' the relay.

-It is another object -ofmy invention-improv-iding a variable time "delay relay having an arrangement for reducing "the time-d'elagwh'en the temperature of theg'lowp'lug is above its normal cold "starting teInperatnr'e.

'There is disclosed in this -application a glow plug ignition 's'ystem 'providecl with a t-im'e delay relay for opening a shunt around aresi's'tmicein series with the glow plug W'henthe glow The system "is preferably provided with a "24 volt battery 20 capable "of delivering 200 amperes for a period of a few milliseconds. One *terminal of this-batteryZOisconnected by'the 'con- "dnct'or -22 to the ground -24. "The other'- terminal of-"the batteryElliscofiniected by the conductor "-ZB-tuone of the contacts o'f-ithe normally' open 'relay'flil. 'Another'of'the contacts of the rel'ay 28 is connected by the conductor 30 to a U- shapeii' bimetal element 3 2-ivhieh in turn is connested by the conductor 14 to one of *the contact-s of amni'htr relay 3'5 which is of the normalls closed type. Anotherof the iconta'cts of The relay 36 is connected by the conductor =38 toth'e gl0w-1$lug element 40 which-"may include Q-COHdUCtOI of p1atinum'alloy. The otherterm'inal or the glow plug element to "is connected to the "ground 24.

"The ignition circuit is energized by =closing the manually operable switch 42- connected in 'series with the 'e'leotromagnet *coil 13 r 0f the relay 28 across the'terminals of the battery 2 8. This causes the :closing of the norma-ll'y "Open :relay plugis-expected toreachits operatingtembera- The closing=0f the re'lay zll penmi'ts azurt-ure. 'The time delay relay includes a nonl e-tit of"' 200--'am10eres to -fiO-W fTUmThB- 'SI GUDG magnetic short (inclined-electrical conductoremcircling the core *of the iron magnetic circuit along side the eleotro'magnet *coil. Thetime "delay re'l'a-y also imilu'cle's a LJ-sh'apel-bimetal elem'ent connected in aeries with "the =g low plug and deflected. by the heating effect o'fthe :rent-to contact and pusha pertion o'f the' relay arma'ture towards the attracted or elo's'e'd circuit/position as the glow plu'g rises tem- 'perature.

Further objects and advantages of the present invention will "be apparent ir'om fihe following description, reference bein "had t'o the accomapaznying drawings, wherein a preferred f'omn of theinvention clearlyflshown.

' In-the nrawings:

Fig. "1 is a view in elevation, partly in secition, of :arela'y embodying enecforrnni anyi'inventio'n.

Fig. 2 isa side View of the -;1 elay shown ll-*1 Fig. 1 taken substantially aa'lo'ng the smegma-a2.

Fig. 3 is a wiring-diagram of 'atfg low plug ignition system embodying "the relay -a's rsnown intFigs. *1 and 2.

While *my time delay relay is applicable to many electrical systems, it is believed that it will be better nniierst'ood by first "describing its use in a glow plug igniti'on'systern. This glow plug ignition system "isiritendedfor use in' s'tarting andniaint'ainin'g "ignition in a rocket engine.

A2 1 "through th-e bonehictor 'ZZ, the battery. 3129, the eon'ductor Z8,.tl 1e eonta'cts 0f the relay 2'8, thefconfinctor fsn, the *U shaped bimeta-l element the conductor 6%, the contacts of :the relay 3-8, the'contluetOr SB an'clthe g'fl'ow 'plug llfl and 'b'adkr to the ground 24. This high current flow fwil-llqnikly "heat the glow plugfitiltto its operating temperature, for example at 250W soo'n as it-his operating temperature is rreaehedgthe cnrr'ent :filowmust he cut flown T to prevent overheating-oi the glo'w plug. "To do this, the :resistance lfi i's iconnected in :shunt with the 'contacts of the relay with its' ter' minals connectingt'to the conductors 34 and-38. The Oblfilil" istOHZpIOX/ iCI'G a reliable "system which under fall conditions will open the relay contacts 38-when the glow plug 5-8 reaches its operating e'tempaaimre 'o'f; iorwexaniple 2500" 1F. .This mustunot be done'stoosocn'or t'heiglow plug will not he ;hot enough f-to immediately start the engine. "This-must mot'be done too iateor the :glloiv plug"will b'urn out. :It therefore neoes'sar'y that "the opening of the relay contacts 36 bedone with considerable accuracy in -timing'.

"The relay 3'75 isprovided with 'an 'electr'0mag-- net operating coil 48 havingone of itst'erminals connected "by the conductor "58 "to the conductor 2'2. "The other terminal of the electromagnet coil 48 is connected by the conductor "52 "with the contact 14 of the relay 54 having a mov able armature I2. The other stationary contact 16 of the relay 54 is connected to the conductor 34. The relay 54 is provided with an electromagnet operating coil 56 having one of its terminals connecting through an adjustable resistance 58 with the conductor 56. The resistance 56 may be adjusted to vary the time delay of the relay 54 by varying the current flow through the coil 56. The other terminal of coil 56 is connected to the conductor 34. The relay 54 including the electromagnet coil 56 and the U-shaped bimetal element 32 in Fig. 3 diagrammatically indicate the physical time delay relay shown in Figs. 1 and 2 which is designed so as to energize at the proper time the electromagnet coil 48 of the relay 36 to open the contacts of the relay 36 to connect the resistance 48 in single series circuit relationship with the glow plug 45 to reduce the current flow to about 25 amperes to prevent the overheating of the glow plug 40.

Referring now more particularly to Figs. 1 and 2, the electromagnet coil 56 is shown encircling a soft iron core 62. This core is mounted in the center of a U-shaped soft iron frame 54 to one leg of which is pivoted the armature 66 also of soft iron material. The core 62 together with the frame 64 and the armature 66 form the magnetic circuit. The armature 66 is connected through an insulating mounting 66 with a movable T-shaped contact arm It carrying a pair of contacts I2. These contacts I2 and contact arm ID are adapted to bridge the contact terminals I4 and I6 each provided with contacts adapted to be contacted by the pair of contacts I2 when the armature 66 is attracted. These contact terminals 14 and 16 are mounted upon the insulating mounting I8.

The position of the contacts I2 relative to the armature 66 is adjusted through the use of a contact adjusting rectangular type spring 86 having its two end portions fastened to two portions of the contact arm I0. A nut 82 is provided which bears upon the center bridge portion of the rectangular type spring so as to hold the contact arm upon the insulating mounting 68 and also to cause the portion of the arm Ill resting upon the mounting 68 to be bent in the amount desired according to the adjustment of the nut 82. It should be noted that the insulated mounting 68 has raised edges so that the contact arm I forms a bridge between these edges and this bridge portion can be deflected by the tightening of the nut 82 to move the contacts I2 closer to the terminal contacts 14 and I6.

The insulation mounting I8 is mounted upon one leg of the frame 64. The frame 64 is provided with an adjusting screw 84 and a lock nut 86 connected to a compression type coil spring 88 within the iron core 62 which in turn connects to a plunger 90 of a nonmagnetic material which freely moves within the iron core 62. The spring 88 extends between the adjusting screw 84 and the plunger 96 Within the core 62 to hold the plunger 90 against the armature 66. The armature 66 is limited in its downward or open circuit position by the armature stop 92 which is adjustably connected by the screw 94 and a suitable slot with the adjacent portion of the frame 64.

In addition to the adjustments already described, this relay includes two additional novel timing features. To reduce the speed of operation of the relay so as to give sufiicient time for the glow plug 46 to heat up to its operating temperature before the resistance 46 is effectively connected into the glow plug circuit, there is provided a heavy copper ring 96 encircling the iron core along side of the electromagnet coil 56. This location of the copper ring is preferred, but it is possible to mount the copper ring encircling other portions of the magnetic circuit. The copper ring retards and opposes the building up of the flux in the magnetic circuit. By the well known law of Lenz, an electromotive force is induced in the copper ring circuit as a result of the building up of the magnetic flux by the energization of the electromagnet coil 56. This copper ring absorbs energy from the flux thereby delaying the rise in the flux to a value high enough to attract the armature 66 until the glow plug 40 has received suflicient current to be heated to its operating temperature. This value, necessary to attract the armature however, is attained within a few milliseconds which allows just sufficient time for the glow plug 46 to attain its operating temperature. At this time, the armature 66 is attracted pushing the plunger upwardly into the core 62 and causing the contact I2 to engage the contacts of the terminal members I4 and I6 to energize the electromagnet coil 48 to cause the opening of the contacts of the relay 36.

The time delay relay shown in Figs. 1 and 2 has an additional feature. There is a possibility that the ignition system may be shut off or deenergized and then turned on or re-energized before the glow plug 46 is allowed to cool to its original normal cold starting temperature. If the same amount of current for the same period of time would be provided Whenever the ignition circuit is energized, there is a possibility that the already hot glow plug might become overheated under this particular circumstance. To prevent this, the U-shaped bimetal element 32 has been provided. This bimetal element 32 includes the bimetal legs I2I and I23 which are connected by a cross bar I25 to provide its U-shaped construction. The cross bar I25 is connected to the bimetals IZI and I23 by rivets and these rivet heads are adapted to bear against the insulating mounting upon the armature 66 when the bimetals I2l and I23 have been heated by the flow of current to the glow plug.

Under this arrangement, the bimetals I2I and I23 will be heated by the current flowing to the glow plug 4!] whenever the glow plug 46 is in operation. The high expanding sides of the bimetals I 2i and I23 face the insulated mounting It so that upon heating, the rivets on these bimetals will bear against the insulated mounting 68 with increasing force as the temperature of the glow plug 46 increases to assist the electromagnet coil 56 and the magnetic circuit to attract the armature 66 more quickly. When the igni-' tion circuit is de-energized, the bimetals I2! and I23 will cool as the glow plug 40 cools. In this way, the time delay of the relay 54 is reduced as the temperature of the glow plug increases.

A copper plate I2! is mounted on the insulating mounting I8 between this mounting and the U-shaped bimetal element 32. This copper plate I2? shields the frame 64 from the magnetic field surrounding the U-shaped bimetal element 32 produced especially when this element carries the initial 200 ampere current.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. A relay including an electromagnetic coil, a magnetic iron circuit associated with said coil including a core and a frame and an armature, an electrothermal means mounted on said frame, said armature having a portion extending into the path of movement of the electrothermal means, and a plate of a nonmagnetic electrical conducting material located between said electrothermal means and said frame and having a sufilcient area to shield said frame from said electrothermal means.

2. A relay including an electromagnet coil, a magnetic iron circuit associated with said coil including a normally open armature, an electrothermal means having an operative connection with said armature and operative to move the armature in a closing direction upon an increase in temperature to adjust the open position of the armature for automatically controlling the time delay, and an electrical heating circuit connected in series with said electromagnet coil and associated with said electrothermal means to heat the electrothermal means and move the armature toward the closed position in proportion to the heating effect of the current flowing through the coil.

3. A relay including an electromagnet coil, a magnetic iron circuit associated with said coil including a normally open armature, a movable stop means cooperating with said armature for setting the limit of opening of said armature, an electrothermal means operatively connected to said stop means and having its temperature responsive expansion directed in the direction to move the stop means to move the armature toward the closed position to automatically control the time delay, and an electrical heating circuit connected in series with said electromagnet coil and associated with said electrothermal means to heat the electrothermal means to move the stop means and the armature toward the closed position in proportion to the heating efiect of the current flowing through the coil.

4. A relay including an electromagnetic coil, a magnetic iron circuit associated with said coil including a core and a frame and an armature, an electrothermal means mounted upon said frame, an electrothermal means having an operative connection with said armature and operative to move said armature upon an increase in temperature, said electrothermal means being mounted on the opposite side of said plate from said frame, an electrical heating circuit energized coincidentally with said electromagnet coil for heating said electrothermal means to move the armature, said plate having a sufficient are-a located to shield said frame from the magnetic field established around said electrothermal means by the flow of energy through said heating circuit.

5. A relay including an electromagnetic coil, a magnetic iron circuit associated with said coil including a core and a frame and an armature, an electrothermal means mounted upon said frame, an electrothermal means having an operative connection with said armature and operative to move said armature upon an increase in temperature, said electrothermal means being mounted on the opposite side of said plate from said frame, an electrical heating circuit connected in series with said electromagnet coil and associated with said electrothermal means to heat the electro-- thermal means to move the armature, said plate having a sufficient area located to shield said frame from the magnetic field established around said electrothermal means by the flow of energy through said heating circuit.

WALTER LYMAN CHURCH.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,761,772 Carpenter June 3, 1930 1,785,852 Wilms Dec. 23, 1930 2,285,560 Bonanno June 9, 1942 2,457,617 Walle Dec. 28, 1948 2,482,955 Wilson Sept. 27, 1949 

